小型哺乳類動物感染發熱伴血小板減少綜合症病毒之分子檢測

Abstract

發熱伴血小板減少綜合症（Severe fever with thrombocytopenia syndrome, SFTS）是一種新興之蜱媒傳染病，2009年首次於中國大陸河南省病患血液中分離出病毒，主要流行國家為中國、日本和韓國，由於國際間往來頻繁，疾病可能從鄰近國家傳播至臺灣。過去研究於微小扇頭蜱、畜牧場之牛和羊及野生動物檢測到發熱伴血小板減少綜合症病毒（severe fever with thrombocytopenia syndrome virus, SFTSV），2019年北部地區與2022年東部離島地區各出現一例本土確診個案，顯示臺灣有疾病感染之風險。SFTSV在自然界中循環傳播的機制尚不清楚，透過實驗和野外調查研究證實長角血蜱為主要病媒，可經卵傳播與跨蟲期傳播，長角血蜱宿主相當廣泛，主要為家禽、家畜、老鼠、鳥類及人類，多篇研究在這些動物中檢測出SFTSV，其中中國山東省囓齒類動物SFTSV RNA陽性率為1.0%、臭鼩為2.6%，亦於浙江省赤背條鼠中分離出與病患序列相似的病毒株，顯示小型哺乳類動物是SFTSV之潛在宿主，因此了解SFTSV在臺灣小型哺乳類動物中流行之情形是相當重要的。本研究2023年6月於臺東縣以及2023年2月至9月於臺灣北、中、南、東部地區置放鼠籠進行誘捕，捕獲之小型哺乳類動物以外部形態特徵鑑定物種，並利用巢式反轉錄聚合酶連鎖反應（Nested RT-PCR）增幅SFTSV M片段基因。臺東縣共捕獲59隻小型哺乳類動物，挑選其脾臟與肺臟組織進行檢測，結果皆為陰性，臺灣北、中、南、東部地區共捕獲349隻小型哺乳類動物，分別檢測了236和143個肺臟、腎臟樣本，無檢測出陽性，結果顯示臺灣民眾透過接觸小型哺乳類動物而感染SFTSV之風險較低，此外於蘭嶼青青草原上所採集之蜱蟲根據外部形態鑑定為長角血蜱或日島血蜱，分子鑑定結果為日島血蜱，目前尚不清楚其是否能傳播SFTSV，由於本研究樣本限制無法進行檢測，建議未來研究能進一步地探討。

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease. Severe fever with thrombocytopenia syndrome virus (SFTSV) was first isolated from patients in Henan province, China, in 2009. China, Japan and Korea were main epidemic countries. Due to international trade and travel, this disease occurred in nearby countries may spread to Taiwan. Previous investigations have established the presence of SFTSV in Rhipicephalus microplus, cattle, goats, sheep and wildlife in Taiwan. Two indigenous cases of SFTS were reported in 2019 and 2022, respectively. Therefore, people in Taiwan are at risk of infection. The natural transmission mechanisms of SFTSV remain elusive. Experimental and field studies have demonstrated that Haemaphysalis longicornis serves as a vector and transmits the virus through transovarial and transstadial transmission. The primary hosts of H. longicornis include poultry, domestic animal, rodents, birds and humans, all showing evidence of SFTSV detection. The positivity rate was 1.0% for rodents and 2.6% for house shrews in China. Further, the viral sequences isolated from rodents (Apodemus agrarius) were highly similar to those obtained from patients in China, suggesting small mammals as potential hosts for SFTSV. It’s crucial to clarify the prevalence of SFTSV in small mammals in Taiwan. In this study, we conducted a small mammals capture survey in Taiwan in 2023. Captured small mammals were identified by morphological characteristics and nested reverse transcription polymerase chain reaction (Nested RT-PCR) was used to amplify the SFTSV M segment gene. All of spleen and lung samples from 59 small mammals in Taitung and 236 lung and 143 kidney samples from 349 small mammals in the northern, central, southern, and eastern regions of Taiwan were investigated. We found no positive samples of SFTSV genes. Consequently, our findings suggest a low potential risk of SFTS in Taiwan. Furthermore, ticks collected from Green Green Grassland in Lanyu were morphologically identified as H. longicornis or H. mageshimaensis. The application of the molecular identification technique revealed that the specimens can be classified as H. mageshimaensis. It is unknown whether H. mageshimaensis can transmit SFTSV, and due to the limitation of the tick samples, further investigation is warranted for future research endeavors.